Dewaxing hydrocarbon oils



Patented Oct. 6, 1936 LIV STAT-S DEWAXING HYDROCARBON OILS Eugene C. Herthel, Flossmoor, Ill., assignor to Sinclair Refining Company, New York, N.:Y., a corporation of Maine No Drawing. Application July 5, 1934, Serial No. 733,858

7 Claims.

This invention relates to improvements in the dewaxing of hydrocarbon oils, more particularly to the dewaxing of petroleum stocks in the manufacture of lubricating oils. The invention pro- 5 vides improved diluents the use of which makes possible improvements in both the economy and the efficiency of the dewaxi'ng operation.

In conventional dewaxing. operations, the stock to be dewaxed is diluted with a diluent such as petroleum naphtha, this stock mixture is chilled to precipitate the wax and the precipitated wax is separated from the chilled stock mixture at low temperature. Recently it has been proposed to use liquid propane, methyl acetate, and blends of benzol and acetone, benzol, acetone and toluol, and benzol and methyl acetate as diluents in such operations.

The improved diluents of this invention comprise the valeric alkyl esters, the butyric alkyl esters, the propionic alkyl esters and the caprylic alkyl esters higher .boiling than the corresponding ethyl esters and include particularly the valeric propyl esters, normal propyl valerate and iso propyl valerate, and the Valerie butyl esters, normal butyl valerate and secondary butyl valerate.

.The improved diluents of this invention have several advantages. Some of these advantages are enjoyed, to some extent, by other diluents hitherto proposed. All of these several advantages are, however, enjoyed in combination by the diluents of this invention.

The ratio of wax solubility to oil solubility in the diluents of this invention diminishes markedly at low temperatures; that is, the diluents of this invention exhibit a marked selectivity for oil over wax at low temperatures, from F. to -40 F. for example. The diluents of this invention are in this respect superior to most other diluents hitherto proposed; they are in this respect approximately equal to blends of benzol and acetone. This advantage of the diluents of this invention is reflected, in one aspect, by the temperature to which the stock mixture must be chilled to produce a product of given pour test from a given stock. With the diluents of this invention it is possible to produce products of 0 F. pour test from stocks having a viscosity up to about 80 seconds at 210 F. by chilling to about F. and from stocks of substantially higher viscosity by chilling, for example, to about 20 F. or -30 F.

The diluents of this invention have relatively high solvent capacity for oil at low temperatures as well as'at higher temperatures. The diluents of this invention are in this respect superior, for example, to blends of benzol and acetone. This 011 solvent capacity of the diluents of this invention minimizes separation of oil at low temperatures and assists in effecting a sharp separation between oil and wax.

The wax precipitated from stock mixtures including the diluents of this invention is in a condition such that it is readily separated from the fluid stock mixture by filtration without requiring more than moderate pressures, and such that it is well adapted for purification by washing or recrystallization operations. The Wax is apparently precipitated from such stock mixtures in a well crystallized condition. This characteristic of the diluents of this invention, in conjunction with their high solvent capacity for oil at low temperature, makes it possible to produce directly Wax of relatively high melting point.

The maximum proportions of the diluents of this invention normally required, from 150% to 300% by volume on the stock to be dewaxed for example, are moderate, approximating, for'exe ample, from 40% to 60% of the volume of blends of benzol and acetone required in comparable instances. I

The diluents of this invention have noydetrimental efiect upon either oil or wax, an advantage also enjoyed, for example, by petroleum naphthaand liquid propane.

The diluents of this invention can be used in conventional apparatus. Special apparatus, high pressure apparatus such as that required for use with liquid propane for example, is not required.

Distillation. equipment corresponding to that used in the conventional recovery of petroleum naphtha can be used to recover the diluents of this invention from the stock following separation of wax. The diluents of this invention are insoluble in water and can be stripped from lubricating oil mixtures by distillation with steam at temperatures not exceeding 400 F. The relatively high boiling range of the diluents of this invention also assists in minimizing losses of the diluent.

Because of the relatively high solvent capacity for oil of the diluents of this invention, they may be used with advantage without admixture with other diluents, such as benzol for example. Benzol, for example, is conventionally used in diluent blends to increase the solvent capacity of the blend for oil at low temperature because some other component of the blend, acetone or methyl acetate for example, has very little solvent capacity for oil at the temperature of wax separation, but benzol also increases the solvent capacity of the blend for wax. The diluents of this invention are not subject to this limitation. They may, however, be used in conjunction with other diluents such as benzol, petroleum naphtha or lower boiling hydrocarbons.

The diluents of this invention may be used in blends including solvents for asphaltic matter, such as carbon disulfide, toluol, carbon tetrachloride or pyridine. Such blends operate to hold natural wax inhibitors in solutionthroughout the dewaxing operation enabling the production of dewaxed stocks which can be given finishing treatments without increase of the pour test.

The following examples of operations embodying the use of diluents of this invention willfurther illustrate the invention:

Example 1.-A Mid-Continent overhead long residuum having a viscosity of 120. seconds at 210 F. is diluted with 300% of its own volume of normal butyl valerate, the mixture is chilled to -20 F., about 9.6% of precipitated wax having a melting point of about 134.5 F. is separated from the fluid stock mixture by filtration and the diluent is steam distilled from the fluid stock mixture to produce a dewaxed oil having a pour test of 15 F.

Example 2.A Mid-Continent overhead long residuum having a viscosity of seconds at 210 F. is diluted with 300% of its own volume of iso propyl valerate, the mixture is chilled to --20 F., about 8.1% of precipitated wax having a melting point of about F. is separated from the fluid stock mixture by filtration and the diluent is steam distilled from the fluid stock mixture to produce a dewaxed oil having a pour test of 10 F.

Example 3.--A Mid-Continent overhead long residuum having a viscosity of 120 seconds at '210 F. is diluted with 300% of its own volume ofnormal propyl valerate, the mixture is chilled to -20 F., about 9.1% of precipitated wax having a melting point of about 135 F. is separated from the fluid stock mixture by filtration and the diluent is steam distilled from the fluid stock mixture to produce a dewaxed oil having a pour test of 8 F.

Example 4.A Mid-Continent overhead long residuum having a viscosity of 120 seconds at 210 F. is diluted with 300% of its own volume of secondary butyl valerate, the mixture is chilled to 20 F., about 6.6% of precipitated wax having a melting point of about 136 F. is separated from the fluid stock mixture by filtration and the diluent is steam distilled from the fluid stock mixture to produce a dewaxed oil having a pour test of 8 F.

The diluents of this invention include, in addition to those previously identified, specifically, propyl iso valerate, iso butyl valerate, iso butyl iso valerate, propyl butyrate, propyl iso butyrate, butyl butyrate, iso butyl butyrate, iso butyl iso butyrate, propyl propionate, butyl propionate, iso butyl propionate and butyl caproate.

As used herein, the term pour test is the lowest temperature at which the oil will flow when chilled." without disturbance, determined, for example, in accordance with method D9730 of the American Society for Testing Materials. Viscosities herein are viscosities in seconds Saybolt Universal.

I claim:

1. In the dewaxing of petroleum oils, the improvement which comprises diluting the oil with a diluent comprising an alkyl ester of an organic acid selected from the group consisting of propionic acid, the butyric acids, the valeric acids, and the caproic acids, higher boiling than the corresponding ethyl esters.

2. In the dewaxing of petroleum oils, the improvement which comprises diluting the oil with a diluent comprising a valeric alkyl ester higher boiling than the valeric ethyl esters.

3. In the dewaxing of petroleum oils, the improvement which comprises diluting the oil with a diluent comprising a valeric propyl ester;

4. In the dewaxing of petroleum oils, the improvement which comprises diluting the oil with a diluent comprising a valeric butyl ester.

5. In the dewaxing of petroleum oils, the improvement which comprises diluting the oil with a diluent comprising normal propyl valerate.

6. In the dewaxing of petroleum oils, the improvement which comprises diluting the oil with a diluent comprising iso propyl valerate.

7. In the dewaxing of petroleum oils, the improvement which comprises diluting the oil with a diluent comprising normal butyl valerate.

EUGENE C. I-IERTI-IEL. 

